Electric lamp



Nov. 5, 1 5.

E. ERICH ELECTRIC LAMP Filed June 12 934 [NI/E UR ER N5 T FRZE'DER [EH E 9W1M H75 TTDRNEY Patented Nov. 5, 1935 UNITED STATES ELECTRIC LAMP Ernst Friederlch, Berlin-Charlottenburg, Gervmany, aasignor to General Electric Company,

a corporation of New York Application June 12,

\ In Germany 1934. Serial No. 130,340

June

5 Claims. (Cl. 176-123) My invention relates to electric lamps and more particularly to the type of lamp disclosed in my pending U. S. application Serial No. 660,701, filed March 14, 1933, Pat. No. 1,998,959, in which light is produced by a bombardment of electrons on an incandescible anode.

I have found that in the type of lamp referred to above it is particularly advantageous in many cases to use, instead of a single indirectly heated cathode, a plurality of such cathodes for heating the anode which serves as the light source. In this way a better distribution of the electric load is obtained. The electron current which flows to the anode and therefore the heating of the anode, are intensified without increasing the cathode load. A particular advantage of employing -a plurality of cathodes lies in the fact that it is possible to disposethe said cathodes around the anode which is thereby heated very uniformly on all sides by the electron bombardment from said cathodes. It is thus possible to use a solid body for the cathode instead of a filamentary structure. The crystallization effects of a filament are thus avoided and vaporization is very slight. It is also possible to use for the anode materials which have a high melting point and are diflicult to work into a wire and which for that reason have not been employed in the incandescent lamp industry. Such materials comprise particularly the carbides such as tantalum car bide, niobium carbide, zirconium and hafnium carbide. Carbon may also be employed for the anode. The anode may consist of a block or ball and thereby provide a small source of light of high intensity for projection purposes.

Further features and advantages of my invention will appear from the following detailed description of species thereof.

The drawing is a perspective view of the internal elements of a lamp comprising my invention, the usual bulb being omitted.

Referring to the drawing, an anode l consisting of a spherical block of, for example, 3 mm. diameter, is mounted on a center support wire I I which is'enclosed in an insulating tube l2. The anode III is surrounded by four cathodes I3 which are connected in parallel and heated indirectly. The said cathodes ii are of the knowntype comprising an insulating tube heated by an embedded heater (not shown) and a metallic coating on the insulating tube having a coating ll of an electron emitting material. The cathodes are held in place by a pair of discs l5, I6. The upper disc i5 which consists of insulating material such as mica is mounted on support wires I1, it the lower ends of which are embedded in the stem press It. The lower disc I6; which consists of metal, is mounted on support wires 20, 2| and is electrically connected to the metal layers of: cathodes l3. 5

Portions of leading-in wires 22, 23 are sealed in the stem press IS. The leading-in wire 22 which is connected to the support wire 20, is connected to the negative side of the source of electrical energy. The disc I 5 and cathodes I3 are thereby charged negatively. Four wires 24 (only the front two being shown) lead from the disc It to the enclosed heaters Tnot shown) of the cathodes. The positive ends 25 of the oathode heaters are connected to wires 26, 21 the ends of which are embedded in the stem press IS. The wires 26, 21 are electrically connected to the anode support II by a cross wire 28 and the wire 21 is connected to the positive leading-in wire 23. i

In order to avoid the formation of a black deposit on the walls of the bulb at the high anode temperature, materials such as cryolite, sodium chloride and calcium fluoride may be used as is well known in the incandescent lamp art. One or more grids may be provided between the oathodes and anode to limit the space charge. It the anode is suspended it may under certain circumstances be heated up to its melting point in which case it must be steadily advanced similar to arc 3 lamps.

The lamps can be operated on all suitable voltages. If alternating current is used, the cathodes that are connected to different phases must be shielded from each other, for example, by mica 3:, discs.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. An electric lamp comprising a plurality of electron sources consisting of indirectly heated 40 cathodes and an incandescible anode which is heated to incandescence by electron bombardment i'rom said'cathodes, said cathodes bein disposed around said anode.

2. An electric lamp comprising a plurality of electron sources consisting of indirectly heated cathodes and an incandescible anode consisting of a solid body of refractory material which is heated to incandescence by electron bombardment from said cathodes, said cathodes being 5 disposed around said anode.

3. An electric lamp comprising a plurality of electron sources consisting of indirectly heated cathodes and an incandescible anode consisting of a solid body of refractory metallic carbide each comprising a heater surrounded by a metal 7 tube having a layer of electron emissive material thereon, an incande'scible anode which is heated to incandescence by electron bombardment from said cathodes. said anode being disposed substantially at the center 01' said cathodes, a lead, means electrically connecting one end of each of said cathode heaters and said anode with said lead, a second lead, and means electrically connecting the opposite ends of each of said heaters and said surrounding metal tubes 10 with said second lead.

ERNST FRIEDRICH. 

